


my kinds of madness

by schweet_heart



Series: Merlin Fic [69]
Category: Merlin (TV), Star Trek: The Original Series
Genre: Alien Biology, Alien Gender/Sexuality, Alien Sex, Alien/Human Relationships, Alpha/Beta/Omega Dynamics, Alternate Universe - Star Trek Fusion, Crack Treated Seriously, Crossover, M/M, Mating Cycles/In Heat, Mildly Dubious Consent, Plot What Plot/Porn Without Plot, Xenophobia, remix eligible
Language: English
Status: Completed
Published: 2017-08-27
Updated: 2017-08-27
Packaged: 2018-12-20 17:41:47
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 998
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11925936
Author URL: https://archiveofourown.org/users/schweet_heart/pseuds/schweet_heart
Summary: Star Trek crossover/fusion. Merlin has a secret. (Un)fortunately, Arthur is about to find out what it is.Second place winner for Pornalot 2017 Challenge #3 (Kink Link).





	my kinds of madness

**Author's Note:**

> **WARNINGS:** Alien biology, alien/human sex, mildly dubious consent (heat-related), vague references to xenophobia, crack taken seriously.
> 
>  **Kinks:** A/B/O, Tenderness  
>  **Tropes:** Crossover, Forced Proximity  
>  **Words:** Gossamer, Onyx, Stallion.
> 
> Title comes from this exchange in the ST:TOS episode, Amok Time: 
> 
> SPOCK: _Captain, there is a thing that happens to Vulcans at this time, almost an insanity, which you would no doubt find distasteful._  
>  KIRK: _Will I? You've been most patient with my kinds of madness._

 

Merlin’s broken moan wakes Arthur on their second day of shore leave, and for a moment he thinks that he’s still dreaming. As he blinks himself awake, however, the sound comes again, and beside him on the cave floor Merlin tosses in his sleep, mouth open, his pale face shining with sweat.  
  
“Merlin?” Arthur says, sitting up. “Are you all right?”  
  
Merlin stirs, opening his eyes into slits then wincing as if he regrets it. He’s clearly conscious, but only just, his whole body shaking like a leaf. Reaching out, Arthur brushes the damp fringe from his forehead.  
  
“Can you hear me?”  
  
“Mmnn,” Merlin groans. He leans into Arthur’s touch like a cat, eyes closing. “It burns.”  
  
“What burns?”  
  
“It _burns_.” As if to emphasise the point, Merlin shoves off his blanket, revealing slim hips and – of all things – a long, hairless tail that is lashing against the rock.  
  
Arthur sits back on his heels. Suddenly it's obvious that this isn’t an ordinary fever. Merlin is hard in his trousers, humping vainly at the air in search of friction, the flushed head of his cock just visible beneath his waistband. He also has a _tail_. Arthur swallows hard.  
  
“Merlin,” he says slowly. “Tell me what’s wrong.”  
  
“Can’t,” Merlin moans. “You’ll hate me.”  
  
“I won’t hate you.” Arthur tries to sound calm. He had known Merlin was born off-world, but not— he hadn’t known about _this_. “Are you— what are you?”  
  
“Katze.” Merlin’s voice is wretched. He turns his face away from Arthur, shoulders hunched. “Half, on my father’s side.”  
  
It makes a grim kind of sense. The Katzen are a playful, curious species, with a fairly rigid social social structure. The Alphas are the ones in charge, while the Omegas…  
  
“You’re in heat, aren’t you?”  
  
Merlin can only nod, and Arthur curses every Earth deity he can think of, plus some from the rest of the Federation for good measure. Damn it, he _won’t_ lose Merlin.  
  
“Don’t tell me,” he says. “You only fuck once every seven years.”  
  
Merlin lets out a weak snort. “That’s Vulcans,” he says, then shudders as another spasm runs through him. “For us, it’s every four— or thereabouts. Figured I had m-more time.”  
  
“That’s why you didn’t want to come camping,” Arthur realises, mentally kicking himself. He had been annoyed by Merlin’s standoffishness, but now it was obvious why he’d hesitated: he’d made other plans. “You had someone waiting for you. Your mate?”  
  
“Not exactly.” Merlin’s breathing is becoming laboured, his knuckles white. “There’s a place— in London. S’posed to be a secret, but they have t-them in most space ports now, since— since.”  
  
Since the Omega Emancipation Act, he meant. It had been big news on Earth at the time, as it meant that Katzenwelt was finally eligible to join the Federation. Arthur’s father had been livid.  
  
“All right,” Arthur says, getting to his feet. He begins to divest himself of his clothing, stripping briskly before he can think better of it. “I realise this isn’t what you’d have chosen, but I’m afraid your options are rather limited at the moment. We’re the only people for miles, and I don’t think you’re going to last much longer.”  
  
“You c-can’t be serious.”  
  
“Does it work with humans?” Arthur asks, ignoring this statement. “Like, does it have to be with another Katzen, or will anyone do?”  
  
“Doesn’t matter.” Merlin shivers. “God, Arthur, don’t— you don’t know what you’re offering. This is dangerous.”  
  
“You won’t hurt me.” Arthur hopes he sounds more confident than he feels. He steps out of his pants and pauses, nerving himself to do the same for Merlin. Aside from the tail, Merlin’s… equipment looks roughly as he would expect, thankfully; this is hardly the time for an anatomy lesson. “Do you have any…?”  
  
Merlin shakes his head. “Don’t need it,” he gasps, spreading his legs in what looks like an unconscious gesture. His hole is already glistening, something like pre-cum moistening the cleft, and Arthur feels the tug of lust deep in his groin. He’d been hard since before Merlin started moaning, but this – this is better than what he’d been dreaming about in the first place. “Arthur…”  
  
“I’m here.” Kneeling, Arthur pushes Merlin’s legs further apart, sliding a pillow beneath him. They’re well beyond taking things slow at this point, but he tries to be gentle anyway, positioning himself carefully before pressing inside. Merlin lets out a low hiss, arching his back.  
  
“Yes! _Arthur_.”  
  
Arthur bottoms out, steadying Merlin with a hand on his hips. “Easy,” he murmurs. “I’ve got you.”  
  
Merlin’s skin is hot against his own, his usually blue irises like onyx: pure pupil. His hands are gripping the bedroll too tightly, but his eyes are fixed on Arthur’s as he moves, his desperation – and his trust – almost palpable.  
  
“Harder,” he begs, finally. “Please, I need— ”  
  
“Yeah,” Arthur breathes back. “Yeah, come on.”  
  
They rock together in tandem. Merlin’s tail nudges between Arthur’s thighs and Arthur jolts as it penetrates, the delicate tip brushing lightly against his rim before dipping inside.  
  
“What—” He lets out a strangled sound as the thing probes deeper, inflaming the sensitive nerve-endings with a gossamer touch. He didn’t— he hadn’t thought— “Oh, _fuck_.”  
  
He comes, spurting inside Merlin, but the sensation doesn’t stop, rolling through him like a tidal wave and drowning out all thought. Greedily, Merlin keeps moving, milking him through the endless aftershocks, his tail flicking against that perfect spot until Arthur is wracked blind with agonising pleasure.  
  
When it’s over, Arthur lies limp on Merlin’s chest and tries to speak.  
  
“What– the hell– was that?”  
  
“I tried to warn you.” Merlin’s voice is sleepy, his hand soft in Arthur’s hair. “I’m told we can be quite insatiable lovers.”  
  
“I’ll say,” Arthur grumbles, and Merlin laughs.  
  
“I’ll take that as a compliment,” he says, twining his arms around Arthur’s body. He pets Arthur's heaving flank the way he might a blowing stallion. “And Arthur?”  
  
“Hmm?”  
  
“We also mate for life.”


End file.
